Communication method of a terminal and an access point for multi-user transmission opportunity (txop) power saving

ABSTRACT

Provided is a terminal and an access point in an active mode for multi-user transmission opportunity (TXOP) power saving that may decrease power consumption by changing an operation state of the terminal from an awake state to a sleep state if there is no stream of data to be transmitted during a TXOP duration.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This present application is a continuation of U.S. patent applicationSer. No. 14/183,814 filed Feb. 19, 2014, which is a continuation of U.S.patent application Ser. No. 13/211,398 filed Aug. 17, 2011, now U.S.Pat. No. 8,681,675, issued Mar. 25, 2014, which claims the benefit under35 U.S.C. §119(e) of U.S. Provisional Application No. 61/412,489, filedon Nov. 11, 2010, and U.S. Provisional Application No. 61/417,528, filedon Nov. 29, 2010, both of which were filed in the U.S. Patent andTrademark Office, and the benefit under 35 U.S.C. §119(a) of IndiaPatent Application No. 2361/CHE/2010, filed Aug. 17, 2010, in theIntellectual Property Office of India, and Korean Patent Application No.10-2011-0022324, filed on Mar. 14, 2011, in the Korean IntellectualProperty Office, the entire disclosures of which are incorporated hereinby reference for all purposes.

BACKGROUND

1. Field

The following description relates to a communication method of aterminal and an access point in an active mode for multi-usertransmission opportunity (TXOP) power saving.

2. Description of Related Art

Mobile terminals such as smart phones allow a user to simultaneouslyperform a variety of functions. The functions include, for example,making a call, playing a motion picture, playing a music file, viewing adigital multimedia broadcasting (DMB), a digital camera function,Bluetooth, wireless Internet access, and the like, using a singledevice. These functions can consume a great deal of power.

In addition, as the data rate of mobile communication networks,Bluetooth, wireless Internet, and the like, increases, the powerconsumption of a terminal also increases. Accordingly, a need for a highcapacity battery for a terminal also increases.

In general, the development of a battery capacity has increased at aslower pace in comparison to the development of the speed ofcommunication technologies. As a result, it is becoming more difficultto satisfy the power consumption of the terminal by increasing thebattery capacity alone. Accordingly, there is a desire for acommunication method that may decrease the power consumption of aterminal.

SUMMARY

In one general aspect, there is provided a communication method of aterminal in a wireless network comprising an access point and aplurality of terminals, the method including generating a power savingmode indicator based on whether the terminal supports a power savingmode for a transmission opportunity (TXOP) duration, transmitting thepower saving mode indicator to the access point, receiving, from theaccess point, information used to determine an operation state of theterminal in the power saving mode, and determining the operation stateof the terminal in the power saving mode based on the information,wherein the TXOP duration corresponds to a time duration in which theaccess point obtaining a TXOP with respect to a channel simultaneouslytransmits data streams to a group of terminals.

The transmitting may comprise transmitting a frame comprising the powersaving mode indicator while the terminal is performing association withthe access point.

If the terminal supports the power saving mode, the power saving modeindicator may have a first logic value, and if the terminal does notsupport the power saving mode, the power saving mode indicator may havea second logic value.

The method may further comprise verifying a power saving mode indicatorof the access point that is received from the access point, wherein thepower saving mode indicator of the access point comprises informationabout whether the access point is capable of supporting the power savingmode with respect to the terminal.

The method may further comprise transmitting, to the access point,information indicating the operation state of the terminal.

The determining may comprise changing the operation state of theterminal based on information received from the access point, and basedon whether the terminal supports the power saving mode.

The changing may comprise changing the operation state of the terminalto one of an awake state and a sleep state based on the informationreceived from the access point.

The information received from the access point may comprise at least oneof a group identifier (ID) of a group comprising the terminal,information indicating whether a data stream corresponding to theterminal is transmitted from the access point during the TXOP duration,and information indicating whether there is an additional data stream tobe transmitted to the terminal during the remainder of the TXOPduration.

In another aspect, there is provided a communication method of an accesspoint in a wireless network comprising the access point and a pluralityof terminals, the method including receiving information indicatingwhether each of the terminals supports a power saving mode for atransmission opportunity (TXOP) duration, transmitting, to at least oneterminal that supports the power saving mode from among the plurality ofterminals, information used to determine an operation state of the atleast one terminal, receiving information indicating the operation stateof the at least one terminal that is determined by the at least oneterminal based on the transmitted information, and simultaneouslytransmitting data streams to the terminals during the TXOP durationbased on information indicating the operation state of the at least oneterminal, wherein the TXOP duration corresponds to a time duration inwhich the access point obtaining a TXOP with respect to a channelsimultaneously transmits data streams to a group comprising the at leastone terminal.

The method may further comprise transmitting information about whetherthe access point is capable of supporting the power saving mode withrespect to the terminals, or information about a support capability ofthe access point for the power saving mode.

The information about whether the access point is capable of supportingthe power saving mode with respect to the terminals may be included in apower saving mode indicator of the access point and may be based onwhether the access point is capable of supporting the power saving mode.

The receiving may comprise receiving, from each of the terminals, aframe comprising a power saving mode indicator indicating whether eachof the respective terminals supports the power saving mode while each ofthe terminals is performing association with the access point.

The method may further comprise transmitting, to the terminals, a TXOPsetting frame comprising information about the TXOP duration, whereinthe TXOP setting frame comprises information about a service set or acell in which the terminals are included and information about thegroup, and is generated such that it is capable of being decoded by botha terminal supporting the power saving mode and a terminal notsupporting the power saving mode.

The simultaneously transmitting may comprise simultaneously transmittingthe data streams to terminals that are in an awake state for the TXOPduration, or buffering a data stream to be transmitted to a terminalthat is in a sleep state.

The information used to determine the operation state of the at leastone terminal may comprise at least one of a group identifier (ID) of agroup comprising the at least one terminal, information indicatingwhether a data stream corresponding to the at least one terminal istransmitted from the access point during the TXOP duration, andinformation indicating whether there is an additional data stream to betransmitted to the at least one terminal during the remainder of theTXOP.

In another aspect, there is provided a computer-readable storage mediumcomprising program instructions to cause a processor to implement acommunication method of a terminal in a wireless network comprising anaccess point and a plurality of terminals, the method includinggenerating a power saving mode indicator based on whether the terminalsupports a power saving mode for a transmission opportunity (TXOP)duration, transmitting the power saving mode indicator to the accesspoint, receiving, from the access point, information used to determinean operation state of the terminal in the power saving mode, anddetermining the operation state of the terminal in the power saving modebased on the information, wherein the TXOP duration corresponds to atime duration in which the access point obtaining a TXOP with respect toa channel simultaneously transmits data streams to a group of terminals.

In another aspect, there is provided a terminal that operates in anactive power saving mode, the terminal including a receiver configuredto receive a data frame from an access point (AP), the data framecomprising a group ID indicating whether the terminal is included in agroup that is served by the AP, and a controller configured to control apower saving mode of the terminal based on whether the terminal isincluded in the group ID.

The data frame may further comprise an indicator that indicates whetherthe terminal is included in a group that is to receive data from the APduring a transmission opportunity (TXOP) obtained by the AP.

The indicator may comprise a number of state time space (N_(STS))included in a very high throughput signal (VHT-SIG) field of the dataframe.

The data frame may further comprise a more data bit (MDB) indicatingwhether transmission of data to the terminal is completed for theremainder of the TXOP duration.

The MDB may be included in a media access control (MAC) header of thedata frame.

In response to the data frame comprising an indicator indicating thatthe terminal is included in the group served by the AP, and the dataframe comprising a N_(STS) field indicating that the terminal is toreceive data during a TXOP obtained by the AP, the controller may befurther configured to operate the terminal in an active state in whichthe terminal listens for a next data frame.

In response to the data frame comprising an indicator indicating thatthe terminal is included in the group served by the AP, the data framecomprising a N_(STS) field indicating that the terminal is to receivedata during a TXOP obtained by the AP, and the data frame comprising aMDB bit indicating that the AP has no more data to be transmitted to theterminal during the TXOP, the controller may be further configured tooperate the terminal in sleep state in which the terminal does notlisten for a next data frame, after the terminal is finished receivingthe data included in the frame.

The terminal may further comprise a transmitter configured to transmit,to the AP, a data frame comprising a power saving mode indicator thatindicates whether the terminal is capable of operating in the powersaving mode for a TXOP duration.

The power save mode indicator may be included in a capability/supportfield of an association request frame.

The receiver may be further configured to receive, from the AP, a beaconframe comprising an information element or a capability element thatindicates whether the AP is capable of supporting power saving mode fora TXOP duration.

Other features and aspects may be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of an operation state and anoperation of a terminal in a transmission opportunity (TXOP) powersaving mode.

FIG. 2 is a flowchart illustrating an example of a communication methodof a terminal.

FIG. 3 is a flowchart illustrating an example of a communication methodof an access point.

FIG. 4 is a diagram illustrating an example of a TXOP setting frame anda TXOP duration.

FIG. 5 is a diagram illustrating an example of truncation of a TXOPduration.

FIG. 6 is a diagram illustrating an example of a terminal.

Throughout the drawings and the detailed description, unless otherwisedescribed, the same drawing reference numerals will be understood torefer to the same elements, features, and structures. The relative sizeand depiction of these elements may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. Accordingly, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be suggested to those of ordinary skill inthe art. Also, description of well-known functions and constructions maybe omitted for increased clarity and conciseness.

In various examples, a terminal may correspond to a single-usermultiple-input multiple-output (SU-MIMO) terminal or a multi-user MIMO(MU-MIMO) terminal.

FIG. 1 illustrates an example of an operation state and an operation ofa terminal in a transmission opportunity (TXOP) power saving mode.

A terminal that receives data from an access point may maintain a powermanagement mode or an operation mode, as an active mode, in order toreceive a packet or a frame transmitted to the terminal. Also, todetermine whether there is a packet or a frame to be transmitted to theterminal, or to overhear a packet to be transmitted to another terminal,the terminal may operate in the active mode.

If there is no transmission of data corresponding to the terminal, or ifthe transmission of data to the terminal is terminated, it is possibleto save power by adjusting the power management mode of the terminal.

Referring to FIG. 1, a power management mode of terminals includes anactive mode 110 and a power saving mode 120.

In the active mode 110, a terminal may continuously operate to transmitand receive data to and from an access point. In the power saving mode120, the terminal may enter into a state, for example, a sleep state 160in which the terminals conserve power. To enter into the power savingmode 120, the terminal may transmit information about an operation stateof the terminal to the access point using a one or more bits of acontrol field of a Media Access Control (MAC) header.

The terminals operating in the active mode 110 may be divided intoterminals that operate in a non-TXOP power saving mode 130 and terminalsthat operate in a TXOP power saving mode 140.

A terminal operating in the non-TXOP power saving mode 130 may maintainan awake state 150 without a separate operation for the power saving.Accordingly, the terminal operating in the non-TXOP power saving mode130 may continuously consume power during a receive standby time that isused to wait for receiving a packet that is transmitted to the terminal.

A terminal operating in the TXOP power saving mode 140 may change anoperation state to the awake state 150 or to the sleep state 160 (alsoreferred to as a doze state) based on whether a predetermined criterionis satisfied.

For example, the predetermined criterion for a terminal may include aplurality of criteria such as a first criterion, a second criterion, anda third criterion. In this example, the first criterion is satisfied forthe terminal if a group identifier (ID) of a group indicates that theterminal is not a member of the group.

The second criterion is satisfied if the group ID of the group indicatesthat the terminal is a member of the group, however, a data streamcorresponding to the terminal is not to be transmitted from the accesspoint during a TXOP. In this example, to indicate that a data streamcorresponding to the terminal is not to be transmitted from the accesspoint during the TXOP, a number of state time space (N_(STS)) includedin a very high throughput signal (VHT-SIG) field of a framecorresponding to the terminal may be set to a predetermined value, forexample, a value of ‘0’.

The third criterion is satisfied if the terminal receives an indicatorindicating that there are no more additional data streams correspondingto the terminal to be transmitted during the TXOP. For example, thegroup ID may indicate that the terminal is a member of the group, theN_(STS) may indicate that there is a frame to be transmitted to theterminal during the TXOP. The terminal may receive a data frame from theAP during the TXOP. The data frame may include an indicator thatindicates that there is no more data to be transmitted to the terminalduring the remainder of the TXOP. In this example, the access point mayindicate to the terminal that the access point is finished transmittingdata to the terminal during the TXOP.

As an example, the indicator indicating that there is no additional datastream corresponding to the terminal may correspond to a case in which amore data bit (MDB) included in a MAC header of a frame received by theterminal from the access point is set to ‘0’. For example, the MDB ofthe MAC header may be set to ‘0’ to indicate that transmission of thedata stream corresponding to the terminal is completed for thatrespective TXOP duration. As another example, the MDB of the MAC headermay be set to ‘1’ to indicate that there is an additional data stream tobe transmitted to the terminal during the TXOP.

A terminal that has any one of the aforementioned criteria satisfied maysave receive standby power for the remainder of the TXOP duration bychanging an operation state from the awake state 150 to the sleep state160. The TXOP duration indicates a time duration in which the accesspoint transmits data streams to a group of terminals.

In this example, the terminal operating in the TXOP power saving mode140 may save consumption power and receive standby power by changing theoperation state to the awake state 150 or the sleep state 160 for theTXOP duration based on the predetermined criterion. Hereinafter, theTXOP power saving mode 140 may be referred to as a power saving mode.

FIG. 2 illustrates an example of a communication method of a terminal.The communication method of the terminal is described in an example of awireless network including an access point and a plurality of terminals.

Referring to FIG. 2, in 210, the terminal generates a power saving modeindicator based on whether the terminal supports a power saving mode fora TXOP duration. The TXOP duration may correspond to a time duration inwhich the access point obtains a TXOP with respect to a channel tosimultaneously transmit data streams to a group of terminals. While theterminal is performing association with the access point, the terminalmay verify a power saving mode indicator of the access point, that is, apower saving mode indicator that is received from the access point.

In 220, the terminal transmits, to the access point, a frame includingthe power saving mode indicator. For example, the terminal may transmitthe frame to the access point by including the power saving modeindicator in an information element of a capability/support field of anassociation request frame such as described by IEEE 802.11. In responseto a valid acknowledgement (ACK) being received from the access pointwith respect to the frame including the power saving mode indicator, theterminal may operate based on a TXOP power saving mode.

In this example, if the terminal supports the power saving mode, thepower saving mode indicator may have a first logic value, and if theterminal does not support the power saving mode, the power saving modeindicator may have a second log value. For example, the first logicvalue may be ‘1’ and the second logic value may be ‘0’.

In 230, the terminal receives, from the access point, information thatis used to determine an operation state of the terminal in the powersaving mode.

In 240, the terminal determines the operation state of the terminal inthe power saving mode based on information that is used to determine theoperation state of the terminal in the power saving mode that isreceived in 230. The terminal may change the operation state of theterminal based on information received from the access point, forexample, information used to determine the operation state of theterminal that is based on whether the terminal supports the power savingmode.

For example, the information received from the access point may includeat least one of a group ID of a group including the terminal,information indicating whether a data stream corresponding to theterminal is transmitted from the access point during the TXOP, andinformation indicating whether there is an additional data stream to betransmitted to the corresponding to the terminal during the remainder ofthe TXOP.

The terminal may change the operation state of the terminal to one of anawake state and a sleep state based on information that is received fromthe access point. The terminal may change the operation state of theterminal based on whether a predetermined criterion is satisfied. Anexample of the predetermined criterion is described herein withreference to FIG. 1. In 250, the terminal transmits, to the accesspoint, information indicating the operation state of the terminal.

FIG. 3 illustrates an example of a communication method of an accesspoint. The communication method of the access point is described in anexample of a wireless network including the access point and a pluralityof terminals.

The access point may generate a power saving mode indicator includinginformation that indicates whether the access point supports the powersaving mode, and may transmit the power saving mode indicator to theterminals. While performing association with the access point, each ofthe terminals may verify the power saving mode indicator of the accesspoint. The access point may further transmit, to the terminals,information about a support capability of the access point for the powersaving mode.

For example, to inform the terminals about whether the access point iscapable of supporting the power saving mode and information about thesupport capability of the access point, the access point may use aninformation element or a capability element of a probe response frame ora beacon frame. As another example, the access point may use a TXOPpower saving support bit to indicate whether the access point is capableof supporting the power saving mode.

In this example, the access point may generate the power saving modeindicator of the access point based on whether the access point iscapable of supporting the power saving mode, and may transmit the powersaving mode indicator of the access point to the terminals. The powersaving mode indicator may express the TXOP power saving support bitindicating whether the access point is capable of supporting the powersaving mode. The power saving mode indicator may use a predeterminedlogic value. Whether the access point is capable of supporting the powersaving mode is used to indicate whether the access point is capable ofperforming association with the terminal that is operating in the powersaving mode.

Referring to FIG. 1, in 310, the access point receives informationindicating whether each of the terminals supports the power saving mode.The TXOP duration may correspond to a time duration in which the accesspoint simultaneously transmits data streams to a group of terminals.

For example, the access point may transmit, to the terminals, a TXOPsetting frame including information about the TXOP duration. The TXOPsetting frame may include information about a service set or a cell inwhich the terminals are included and information about the group, andmay be generated such that it is capable of being decoded by both aterminal that supports the power saving mode and a terminal that doesnot support the power saving mode. An example of the TXOP setting frameis described with reference to FIG. 4.

In 320, the access point transmits, to at least one terminal supportingthe power saving mode from among the plurality of terminals, informationthat is used to determine an operation state of the at least oneterminal. For example, the information that is used to determine theoperation state may include at least one of a group ID of a groupincluding the at least one terminal, information indicating whether adata stream corresponding to the at least one terminal is transmittedfrom the access point during the TXOP, and information indicatingwhether there is an additional data stream to be transmitted to the atleast one terminal during the remainder of the TXOP.

In 330, the access point receives information indicating the operationstate of the at least one terminal. The operation state may bedetermined by the at least one terminal based on information that isused to determine the operation state of the at least one terminal.After performing association with the terminal, the access point mayreceive information about a current operation state of the terminal andthen determine an operation of the access point.

In 340, the access point simultaneously transmits data streams to theterminals for the TXOP duration. The access point may simultaneouslytransmit data streams based on information indicating the operationstate of the at least one terminal. The access point may simultaneouslytransmit the data streams to terminals that are in an awake state forthe TXOP duration, or may buffer a data stream to be transmitted to aterminal that is in a sleep state if the data stream to be transmittedto the terminal occurs while the terminal is in the sleep state for theremainder of the TXOP duration.

In some examples, the access point may simultaneously transmit datastreams to a plurality of terminals that are included in the group ofterminals that is to receive data during the TXOP. It should beappreciated that simultaneously transmitting does not necessarily meanthat the data streams transmitted to the plurality of terminals startand/or stop at the same time.

FIG. 4 illustrates an example of a TXOP setting frame and a TXOPduration. In FIG. 4, AP is used to indicate an access point and STA isused to indicate a terminal.

Referring to FIG. 4, AP 401 desiring to transmit data to at least oneSTA may be assigned the right to use a channel for a predeterminedduration, for example, a TXOP duration 430 and may exclusively use thechannel during the predetermined duration. In this example, an STA (1)403, an STA (2) 405, an STA (3) 407, and an STA (4) 409 may transmitblock ACKs (BAs) 465, 470, 475, 480, and 485 with respect to a receivedpacket or frame for the TXOP duration 430.

For example, the AP 401 may transmit data to only a single STA or onlyan STA of a predetermined group for the TXOP duration 430.

If there is no additional data to be transmitted to the predeterminedSTA of the group during the remainder of the TXOP duration 430, the AP401 may indicate, that there is no additional data to be transmittedusing a frame or a packet currently transmitted. In this example, the AP401 may not transmit data to the corresponding STA for the remainder ofthe TXOP duration 430.

To indicate whether there is additional data to be transmitted to thecorresponding STA, the AP 401 may use a single bit of a MDB. The MDB maybe included in a preamble of a packet to be transmitted or in a MACheader.

For example, if the MDB is set to ‘0’ for a terminal, this may be usedto indicate that the AP 401 has no more additional data to transmit tothe terminal. Accordingly, the terminal may operate in a power savingmode, that is, in a sleep state during the remainder of the TXOPduration 430 after terminating receiving of a corresponding packet fromthe AP 401, or after transmitting a BA. In this example, if data to betransmitted to the terminal reoccurs after the AP 401 indicates thatthere is no additional data to be transmitted to the corresponding STA,the AP 401 may store the data in a buffer until a subsequent TXOP.

To enable a predetermined STA to occupy a channel for a predeterminedperiod, another STA excluding an STA assigned with a right to access thechannel in a cell or a basic service set (BSS) may avoid the channelaccess for a corresponding TXOP duration. The TXOP duration may be setsuch that all the STAs within the cell or the BSS may avoid the channelaccess for the corresponding TXOP duration.

Hereinafter, an example of a method of setting the TXOP duration 430 bysetting a separate TXOP setting period 410 is described.

The AP 401 may set a time duration of a TXOP with respect to a channel,that is, the TXOP duration 430 by transmitting a TXOP setting frame 420during the TXOP setting period 410.

The TXOP setting frame 420 may include information that is used to setthe TXOP duration 430. The TXOP setting frame 420 may be transmitted ina form that may be overheard by all the STAs within a cell or a BSS, forexample, STAs that have set a power management mode to a power savingmode and STAs that have not set the power management mode to the powersaving mode.

For example, a multi-user precoding scheme and the like may not beapplied to the TXOP setting frame 420. The TXOP setting frame 420 may begenerated such that it is capable of being decoded by all of the STAswithin the cell.

The TXOP setting frame 420 may include information about whether toapply the power saving mode, or a target reception group that is atransmission target of a frame during the TXOP duration 430. Informationthat is associated with the target reception group may include apredetermined group with the same group ID and information indicatingSTAs that are included in the predetermined group. An STA that isexcluded from a corresponding reception group may maintain a sleep stateduring the TXOP duration 430 after receiving the TXOP setting frame 420.

An STA such as STA 1 403 that is included in the target reception groupmay transmit a response frame 460 with respect to the TXOP setting frame420. For example, the response frame 460 may include a portion of or allof the fields included in the TXOP setting frame 420.

Accordingly, hidden nodes not receiving the TXOP setting frame 420 mayset a TXOP. If a plurality of STAs transmit the response frame 460, theSTAs may transmit the response frame 460 according to a predeterminedorder and a predetermined method. For example, the predetermined orderand the predetermined method may be included in the TXOP setting frame420.

Information that is associated with the predetermined group having thesame group ID and the STAs that are included in the predetermined groupmay receive a frame that is transmitted for the TXOP duration 430, inaddition to the TXOP setting frame 420, for example, frames 440 and 450.The TXOP setting period 410 may be used to set the time duration of theTXOP with respect to the channel, for example, the TXOP duration 430.

As an example, in the TXOP setting period 410 for setting the TXOPduration 430, the AP 401 may transmit the TXOP setting frame 420 to theSTA (1) 403, the STA (2) 405, the STA (3) 407, and the STA (4) 409within the cell.

The TXOP setting frame 420 may be used to indicate whether acorresponding STA is to receive a corresponding stream during the TXOPduration 430, or whether to operate in the power saving mode for theduration of the TXOP 430. In the example of FIG. 4, the STA (1) 403, theSTA (2) 405, and the STA (3) 407 are to receive data from the AP 401during the TXOP duration 430.

For example, the TXOP setting frame 420 may include a preamble 421, alegacy signal field (L-SIG) 423, and TXOP setting information 425 forsetting the TXOP duration 430.

Each of the STA (1) 403, the STA (2) 405, the STA (3) 407, and the STA(4) 409 may set the time duration, for example, the TXOP duration 430based on the TXOP setting information. In this example, the TXOPduration 430 is a timer period in which the AP 401 obtaining a TXOP withrespect to a channel to simultaneously transmit data streams to one ormore STAs from the group of the STA (1) 403, the STA (2) 405, the STA(3) 407, and the STA (4) 409.

In this example, each of the STA (1) 403, the STA (2) 405, and the STA(3) 407 are to receive data from the AP 401 during the TXOP duration430. Accordingly, the STA (1) 403, the STA (2) 405, and the STA (3) 407may operate in an active mode for the TXOP duration 430 and may receivea packet or a frame from the AP 401. However, the STA (4) 409 is not toreceive data from the AP 401 during the TXOP duration 430. Accordingly,the STA (4) to 409 may not access a radio channel for the TXOP duration430.

The TXOP setting information 425 may include information that isassociated with a group of STAs to receive data from the AP 401 amongthe STA (1) 403, the STA (2) 405, the STA (3) 407, and the STA (4) 409.Each of the STA (1) 403, the STA (2) 405, the STA (3) 407, and the STA(4) 409 may set the TXOP duration 430 based on the TXOP settinginformation 425.

The STA (1) 403 is to receive data from the AP 401 and may transmit, tothe AP 401, the response frame 460 with respect to the TXOP settinginformation 425. The response frame 460 may prevent entangling of theSTA (1) 403, the STA (2) 405, the STA (3) 407, and the STA (4) 409, forexample, when coverages of a plurality of APs overlap with each other.

If there is no additional data to be transmitted before the set TXOPduration 430 ends, the AP 401 having transmitted data within the TXOPduration 430 may terminate the TXOP duration 430 early. An example inwhich the AP 401 truncates the TXOP duration 430 is described withreference to FIG. 5.

In FIG. 4, it is assumed that the STA (1) 403, the STA (2) 405, and theSTA (3) 407 correspond to STAs that are to receive data from the AP 401,and the STA (4) 409 corresponds to an STA that is not to receive datafrom the AP 401.

The AP 401 may transmit, to each of the STA (1) 403, the STA (2) 405,the STA (3) 407, the STA (4) 409, packets or frames including controlinformation and data. The AP 401 may include information that isassociated with the STAs that are to receive data, in controlinformation of a data frame for the corresponding STAs and therebytransmit the data frame. Because the STA (4) 409 is not to receive datafrom the AP 401 during the TXOP duration 430, the STA (4) 409 mayoperate in the power saving mode for the TXOP duration 430.

For example, information that is associated with a reception group maybe transmitted using a group ID through VHT-SIG fields 442 and 452 offrames 440 and 450 to that are transmitted during the TXOP duration 430.The reception group may indicate a group of STAs that have data to betransmitted from the AP 401 to the STAs.

In some examples, the STA (4) 409 may verify the VHT-SIG field 442 ofthe frame 440 in the TXOP duration 430 and then, verify that there is nodata to be transmitted to the STA (4) 409 and immediately enter into asleep state for the remainder of the TXOP duration 430. The STA (4) 409entering into the sleep state may not overhear a frame or a packet to betransmitted to another STA. The STA (4) 409 may not perform an activereceive operation for receiving a frame or a packet during the remainderof the TXOP duration 430 thereby minimizing power consumption.

The preambles 441 and 451 may be used for one or more of the STA (1)403, the STA (2) 405, the STA (3) 407, and the STA (4) 409 to estimate achannel or to sense a frame or a packet. In this example, each of theVHT-SIG fields 442 and 452 may include a control signal with respect tothe STA (1) 403, the STA (2) 405, and/or the STA (3) 407 which are toreceive data at a very high throughput.

Examples of the control signal include information that is associatedwith a modulation scheme, a channel coding scheme, and the like, withrespect to data included in each of data areas 443, 445, 447, 453, and455 of the frames 440 and 450.

The frame 440 includes the data areas 443, 445, and 447 that are to betransmitted to STA (1) 403, the STA (2) 405, and the STA (3) 407,respectively. The frame 450 includes the data areas 453 and 455 that areto be transmitted to the STA (2) 405 and the STA (3) 407, respectively.

Prior to an end point in time of a packet, transmission of data includedin each data area may be completed, and transmission with respect to acorresponding STA may be completed.

For example, in the first frame 440, the first data area 443 may beterminated when transmission of first data is completed, and the seconddata area 445 may be terminated when transmission of second data iscompleted. In the first frame 440, because transmission of third data isnot completed by an end point in time of the packet, the third data area447 may be terminated at the end point in time of the frame. In theexample of the first frame 440, a pad 444 may be added to a rear of thedata area 443, a pad 446 may be added to a rear of the data area 445.

Each of the data areas 443, 445, 447, 453, and 455 may additionallyinclude a transmission complete message with respect to each data. AnMDB may be used to indicate whether there is data to be additionallytransmitted during the remainder of the TXOP with respect to thecorresponding frame or the corresponding channel. In this example, theTXOP duration 430 may be used as the transmission complete message.

For example, transmission of first data is completed within the firstframe 440 and there is no more data to be transmitted to the STA (1) 401during the TXOP duration 430. In this example, the AP 401 may set an MDBwith respect to the STA (1) 403 as ‘0’. The MDB with respect to the STA(1) 403 may be included in an end portion of the first data area 443 andmay be transmitted to the STA (1) 403.

The STA (1) 403 may receive a packet with the MDB set to ‘0’ anddetermine that there is no more data to be transmitted to the STA (1)403 during the TXOP duration 430. Accordingly, the STA (1) 403 mayoperate in the power saving mode, for example, in the sleep state aftertransmission of the first data is completed, thereby reducing powerconsumption.

In this example, the AP 401 has additional data to transmit to the STA(2) 405. Accordingly, the MDB bit corresponding to the STA (2) 405 isset to indicate that the AP 401 has additional data to transmit to theSTA (2) 405 during the TXOP duration 430. In this example, the ‘1’ bitis used to indicate that there is additional data to be transmitted.However, this is merely for purposes of example, and any desiredcharacter may be used or symbol may be used.

In addition, although transmission of data transmitted to the STA (3)407 is completed in the third data area 447 of the first packet 440,data to be transmitted to the STA (3) 407 remains. In this example, aremaining portion of the third data may be transmitted using the thirddata area 455 of the second frame 450. In this example, the AP 401 mayset the MDB corresponding to the STA (3) 407 as ‘1’.

The STA (1) 403, the STA (2) 405, and the STA (3) 407 may receive aframe or a packet within the TXOP duration 430, and may transmit, to theAP 401, ACK messages or the BAs 465, 470, 475, 480, and 480.

The AP 401 may transmit data to STAs that are included in predeterminedgroups that have the same group ID or a separate STA for the TXOPduration 430.

If there is no more data to be transmitted to a predetermined STA withina predetermined group for the TXOP duration 430, the AP 401 mayindicate, in a currently transmitting frame or packet, that there is noadditional data to be transmitted to the predetermined STA and then, maynot transmit data to the predetermined STA for the remainder of the TXOPduration 430.

As described in various example, the AP 401 may generate an indicatorindicating that there is no more data to be transmitted to apredetermined STA for the TXOP duration 430. For this operation, the AP401 may use a single bit of MDB. For example, if there is no more datato be transmitted to the STA (1) 403, the AP 401 may set the MDB of theSTA (1) 403 to ‘0’. If there is data to be transmitted to the STA (2)405, the AP 401 may set an MDB of the STA (2) 405 to ‘1’.

The MDB may be included in a preamble or a header of a MAC frame to betransmitted to each STA.

If the MDB is set to ‘0’, a terminal may maintain the power saving modeby the end of the TXOP duration 430 after terminating receiving of acorresponding packet, or after transmitting an ACK or a BA with respectto the corresponding packet.

For those STAs that receive an indicator indicating that there is nomore data to be transmitted during the TXOP duration, the AP 401 may nottransmit data to a corresponding STA for the remainder of the TXOPduration 430. In this example, if data to be transmitted to the STA (1)403 reoccurs after indicating that there is no data additional to betransmitted to the STA (1) 403, the AP 401 may buffer the correspondingdata in a buffer until a subsequent TXOP. That is, if data to betransmitted to the STA (1) 403 occurs during the TXOP duration 430, theAP 401 may buffer the data to be transmitted by a subsequent timeduration with respect to the STA (1) 403. In this example, ‘until thesubsequent channel is occupied’ may indicate a subsequent time durationcorresponding to another TXOP, and may indicate a TXOP duration that issubsequent to the TXOP duration 430.

FIG. 5 illustrates an example of truncation of a TXOP duration.

As described above with reference to FIG. 4, an access point maytransmit TXOP sharing, for example, an MU-MIMO data frame 513 to aterminal based on a TXOP setting frame 511. If there is no more data tobe transmitted to the terminal prior to an initially set TXOP duration510 ending, the access point may transmit, to the terminal, a frameindicating an end of the TXOP duration 510 and may truncate the TXOPduration 510. The frame indicating the end of the TXOP duration 510 maybe, for example, a contention free-end (CF-End) frame 515.

If the TXOP duration 510 is truncated, a problem may occur due toterminals in a sleep state for the existing set TXOP duration 510. Theterminals in the sleep state may not receive the frame indicating theend of the TXOP duration 510 and thus, may be unaware that the TXOPduration 510 is truncated. Accordingly, the terminals in the sleep statemay remain in the sleep state until the end of the TXOP duration 510.

In this circumstance, if the access point or terminals in an active modewere to transmit data to the terminals in the sleep state, communicationmay not be properly performed, thereby deteriorating throughput of thewhole network.

As described in various examples, terminals may save power for a TXOPduration by setting a corresponding mode so that an access point maybecome aware of a current state of the terminals desiring to save power.Even though the TXOP duration is truncated, the access point may assumethat a terminal in a power saving mode remains in a sleep state for theend of the initially set TXOP duration and thereby may not transmit datato the corresponding terminal.

To inform the access point about whether the terminal supports the powersaving mode, the terminal may use a power saving mode indicator. Forexample, as described herein with reference to FIG. 1, the power savingmode indicator may be expressed using a separate bit indicating thenon-TXOP power saving mode 130 and the TXOP power saving mode 140.

FIG. 6 illustrates an example of a terminal.

Referring to FIG. 6, terminal 600 is capable of operating in an activepower saving mode. The terminal includes a receiver 610, a controller620, and a transmitter 630.

The receiver 610 may receive a data stream from an access point (AP). Adata frame included in the data stream may include a group ID indicatingwhether the terminal is included in a group that is served by the AP.

As another example, the data frame may include an indicator thatindicates whether the terminal is included in a group that is to receivedata from the AP during a transmission opportunity (TXOP) obtained bythe AP. For example, the indicator may be a number of state time space(N_(STS)) included in a very high throughput signal (VHT-SIG) field ofthe data frame.

As another example, the data frame may include a more data bit (MDB)indicating whether transmission of data to the terminal is completed forthe remainder of the TXOP duration. For example, the MDB may be includedin a media access control (MAC) header of the data frame.

The controller 620 may control a power saving mode of the terminal 600based on the information included in the data frame.

For example, in response to the data frame including an indicatorindicating that the terminal 600 is included in the group served by theAP, and a N_(STS) field indicating that the terminal is to receive dataduring a TXOP obtained by the AP, the controller may operate theterminal 600 in an active state in which the terminal listens for a nextdata frame.

As another example, in response to the frame including an indicatorindicating that the terminal 600 is included in the group served by theAP, and the frame including a N_(STS) field indicating that the terminalis to receive data during a TXOP obtained by the AP, and including a MDBindicating that the terminal 600 is not to receive additional dataduring the remainder of the TXOP obtained by the AP, the controller mayoperate the terminal 600 in sleep state in which the terminal 600 doesnot listen for a next data frame, after the terminal 600 is finishedreceiving the data included in the frame.

The transmitter 630 may transmit, to the AP, a frame comprising a powersaving mode indicator that indicates whether the terminal is capable ofoperating in the power saving mode for a TXOP duration. For example, thepower save mode indicator may be included in a capability/support fieldof an association request frame described by 802.11

As another example, the receiver 610 may receive, from the AP, a beaconframe comprising an information element or a capability element thatindicates whether the AP is capable of supporting power saving mode fora TXOP duration.

In various examples, an access point may transmit at least one frame toa terminal without additional contention after occupying a channel for aTXOP duration. Therefore, it is possible to enhance transmissionefficiency and quality of service (QoS).

In various examples, even though a TXOP duration is truncated before theinitially set TXOP duration ends, it is possible to prevent theefficiency of whole network from decreasing by transmitting data to aterminal that does not operate in a power saving mode and that does notenter into a sleep state.

In various examples, if there is no stream of data to be transmitted toa terminal operating in a power saving mode during a TXOP duration, theterminal may recognize that there is no data stream before an end of theTXOP duration, and may maintain an operation state of the terminal in asleep state for the duration of the TXOP, thereby reducing power.

In various examples, if a predetermined criterion is satisfied, aterminal operating in a power saving mode may change an operation stateof the terminal from an awake state to a sleep state, thereby reducingpower consumption.

Program instructions to perform a method described herein, or one ormore operations thereof, may be recorded, stored, or fixed in one ormore computer-readable storage media. The program instructions may beimplemented by a computer. For example, the computer may cause aprocessor to execute the program instructions. The media may include,alone or in combination with the program instructions, data files, datastructures, and the like. Examples of computer-readable storage mediainclude magnetic media, such as hard disks, floppy disks, and magnetictape; optical media such as CD ROM disks and DVDs; magneto-opticalmedia, such as optical disks; and hardware devices that are speciallyconfigured to store and perform program instructions, such as read-onlymemory (ROM), random access memory (RAM), flash memory, and the like.Examples of program instructions include machine code, such as producedby a compiler, and files containing higher level code that may beexecuted by the computer using an interpreter. The program instructions,that is, software, may be distributed over network coupled computersystems so that the software is stored and executed in a distributedfashion. For example, the software and data may be stored by one or morecomputer readable storage mediums. Also, functional programs, codes, andcode segments for accomplishing the example embodiments disclosed hereincan be easily construed by programmers skilled in the art to which theembodiments pertain based on and using the flow diagrams and blockdiagrams of the figures and their corresponding descriptions as providedherein. Also, the described unit to perform an operation or a method maybe hardware, software, or some combination of hardware and software. Forexample, the unit may be a software package running on a computer or thecomputer on which that software is running.

As a non-exhaustive illustration only, a terminal/device/unit describedherein may refer to mobile devices such as a cellular phone, a personaldigital assistant (PDA), a digital camera, a portable game console, andan MP3 player, a portable/personal multimedia player (PMP), a handhelde-book, a portable lab-top PC, a global positioning system (GPS)navigation, a tablet, a sensor, and devices such as a desktop PC, a highdefinition television (HDTV), an optical disc player, a setup box, ahome appliance, and the like that are capable of wireless communicationor network communication consistent with that which is disclosed herein.

A computing system or a computer may include a microprocessor that iselectrically connected with a bus, a user interface, and a memorycontroller. It may further include a flash memory device. The flashmemory device may store N-bit data via the memory controller. The N-bitdata is processed or will be processed by the microprocessor and N maybe 1 or an integer greater than 1. Where the computing system orcomputer is a mobile apparatus, a battery may be additionally providedto supply operation voltage of the computing system or computer. It willbe apparent to those of ordinary skill in the art that the computingsystem or computer may further include an application chipset, a cameraimage processor (CIS), a mobile Dynamic Random Access Memory (DRAM), andthe like. The memory controller and the flash memory device mayconstitute a solid state drive/disk (SSD) that uses a non-volatilememory to store data.

A number of examples have been described above. Nevertheless, it shouldbe understood that various modifications may be made. For example,suitable results may be achieved if the described techniques areperformed in a different order and/or if components in a describedsystem, architecture, device, or circuit are combined in a differentmanner and/or replaced or supplemented by other components or theirequivalents. Accordingly, other implementations are within the scope ofthe following claims.

What is claimed is:
 1. A method of an access point, comprising:generating a legacy preamble; generating a very high throughput signal(VHT-SIG) field to be transmitted to a terminal subsequent to the legacypreamble, wherein the VHT-SIG field comprises information of whether theaccess point allows the terminal in an active mode to enter a doze stateduring a transmission opportunity (TXOP) duration; generating a mediumaccess control (MAC) frame comprising a MAC header, wherein the MACheader comprises information indicating whether additional data istransmitted to the terminal; and combining the legacy preamble, theVHT-SIG field, and the MAC frame with a corresponding data field.
 2. Themethod of claim 1, wherein the VHT-SIG field comprises a groupidentifier (ID).
 3. The method of claim 1, wherein the VHT-SIG fieldcomprises information of a number of streams intended for the terminal.4. The method of claim 1, further comprising: receiving, from theterminal, information indicating an operation state of the terminal thatis determined based on the VHT-SIG field and the MAC frame.
 5. Themethod of claim 4, further comprising: transmitting a data stream to theterminal during the TXOP duration based on the information indicatingthe operation state of the terminal.
 6. The method of claim 4, whereinthe receiving comprises receiving, from the terminal, a power savingmode indicator indicating whether the terminal supports a power savingmode while the terminal is performing association with the access point.7. The method of claim 1, further comprising: transmitting, to theterminal, a TXOP setting frame comprising information about the TXOPduration.
 8. The method of claim 7, wherein the TXOP setting framecomprises information about a service set or a cell in which theterminal is included and information about a group in which the terminalis included.
 9. The method of claim 7, the TXOP setting frame isdecodable by a terminal supporting a power saving mode and a terminalnot supporting the power saving mode.
 10. The method of claim 1, furthercomprising: transmitting a data stream to the terminal in response tothe terminal being in an awake state for the TXOP duration.
 11. Themethod of claim 1, further comprising: buffering a data stream to betransmitted to the terminal in response to the terminal being in thedoze state.